47 CFR 90.391: Maximum EIRP and antenna height.

(a) C-V2X licensees must limit RSU equivalent isotropically radiated power (EIRP) to 33 dBm. This limit applies to any operation within the 5895-5925 MHz band as follows:

(1) 33 dBm/10 MHz EIRP;

(2) 33 dBm/20 MHz EIRP; and

(3) 33 dBm/30 MHz EIRP.

(b) For purposes of this section, the EIRP is root mean squared (RMS) measured as the maximum EIRP toward the horizon or horizontal, whichever is greater, of the gain associated with the main or center of the transmission beam.

(c) The radiation center of an RSU antenna shall not exceed 8 meters above the roadway bed surface, except that an RSU may employ an antenna with a height exceeding 8 meters but not exceeding 15 meters provided the EIRP specified in paragraph (a) of this section is reduced by a factor of 20 log(Ht/8) in dB where Ht is the height of the radiation center of the antenna in meters above the roadway bed surface. The RSU antenna height must not exceed 15 meters above the roadway bed surface.